Backplane transmission line system

Abstract

A backplane motherboard which mounts a plurality of printed circuit boards and which provides microstrip transmission lines to interconnect the components of an inserted PC board with any of the other inserted PC boards. All transmission lines are terminated at both ends with the characteristic impedance, and the plane of the motherboard is made of a sandwich construction having a ground plane, a Mylar insulating plane, a voltage plane, and outer epoxy surface insulators. The plane sandwich also carries terminal pins for holding additional printed circuit boards.

In view of the above described backplane transmission line system, the following claims are made: 
     
       1. An assembly comprising: a plurality of transmission lines made up of a plurality of etched microstrip traces on at least one outer insulating surface of a backplane, said backplane having at least a ground plane sandwiched between the outer insulating surfaces, and wherein   at least some of said transmission lines are terminated at both ends thereof with their characteristic impedance,   said impedance including a resistance-capacitance network.   
     
     
       2. The assembly of claim 1 wherein said transmission lines are connected to control devices for controlling the signals thereon and said control devices include buffers of the open-collector type, and said resistance-capacitance network, is coupled to a source of potential. 
     
     
       3. The assembly of claim 1 wherein said impedance includes a series resistance-capacitance network. 
     
     
       4. The assembly of claim 1 wherein said impedance includes a series capacitance-resistance network coupled between said transmission line and said ground plane. 
     
     
       5. The assembly of claim 1 wherein said impedance includes a series resistance-capacitance-resistance network coupled between a source of potential and said ground plane with said transmission line coupled to the junction of said capacitance with one of said resistances. 
     
     
       6. The assembly of claim 1 wherein said impedance includes a series resistance-capacitance network coupled between a source of potential and said ground plane. 
     
     
       7. The assembly of claim 1 wherein said transmission lines are connected to control devices for controlling the signals thereon and said control devices include buffers of the Transistor-Transistor Logic type. 
     
     
       8. The assembly of claim 7 wherein said control devices include buffers of the tri-state type. 
     
     
       9. A backplane comprising: a. backplane made of a voltage plane and a ground plane separated by an insulating layer, said voltage plane and said ground plane sandwiched between insulating layers which form a first face and a second face;   b. terminals placed at specific locations on said backplane for electrically connecting points on said first and second faces and points on said voltage plane; and wherein;   c. said first face mounts a plurality of connectors suitable for holding and mounting printed circuit boards;   d. said first and second faces provide microstrip transmission lines which connect similarly located terminal pins on each of said connectors;   e. each of said microstrip lines form a transmission line with the said ground plane or said voltage plane;   f. each end of at least some of said transmission lines being terminated with their characteristic impedance and   g. each said characteristic impedance including a series resistance-capacitance network.   
     
     
       10. The backplane of claim 9, including a plurality of printed circuit boards and means to control the signal on said transmission lines. 
     
     
       11. The backplane of claim 10 wherein said means to control includes buffers of at least the open-collector type. 
     
     
       12. The assembly of claim 11 wherein said resistance-capacitance network includes a first resistance,   a second resistance, and   a capacitance coupled between said first and said second resistances,   said first resistance having its end remote from said capacitance coupled to said voltage plane,   said second resistance having its end remote from said capacitance coupled to said group plane,   said transmission line end coupled to the junction of said first resistance with said capacitance.   
     
     
       13. The assembly of claim 10 wherein said means to control includes buffers of at least the tri-state type. 
     
     
       14. The assembly of claim 13 wherein said resistance-capacitance network includes a capacitance, and   a resistance connected in series with said capacitance,   said series resistance-capacitance network coupled between the end of said transmission line and said ground plane.   
     
     
       15. A backplane having a first face and a second face comprising: a. a laminated structure composed of at least two layers of electrically conductive material and an intervening layer of insulating material; one of said layers forming a ground plane and the other layer a voltage supply plane;   b. electrically conductive terminal pins mounted in columns upon said backplane and for connecting said first face of said backplane at selected points to said second face of said backplane, and also for contacting voltage supply points in said voltage plane;   c. a plurality of connectors mounted upon said first face of said backplane for mounting and connecting printed circuit boards;   d. microstrip conductive lines etched on at least said second face of said backplane, said microstrip lines connecting respective points on at least some of said connectors;   e. terminating impedances coupled to each end of at least some of said microstrip transmission lines;   f. said terminating impedances including a resistance-capacitance network.   
     
     
       16. The backplane of claim 15 further comprising an open collector-type buffer coupled to at least some of said transmission lines, and   said terminating impedances include a series resistance-capacitance network coupled between said voltage plane and said ground plane.   
     
     
       17. The backplane of claim 15 further comprising a tri-state buffer coupled to at least some of said transmission lines, and   said terminating impedances include a series resistor-capacitor coupled between said ground plane and said transmission lines having said tri-state buffer coupled thereto.   
     
     
       18. The backplane of claim 15 further comprising an open collector-type buffer coupled to at least some of said transmission lines, and   said terminating impedances include a series resistor-capacitor-resistor divider connected between said voltage plane and said ground plane for said transmission lines having said open collector-type buffer coupled thereto.   
     
     
       19. In a system for interconnecting a multiplicity of terminals with means to control the voltage and signal condition on the interconnection means, the combination comprising: a backplane including: a. a plurality of connectors for supporting and connecting printed circuit boards;   b. a plurality of microstrip transmission lines for connecting each respective terminal on one connector to respective terminals on at least some of the other connectors;   c. means for terminating at least some of said microstrip transmission lines at both ends thereof to provide the characteristic impedance for each transmission line; and   d. a plurality of printed circuit boards including control devices which connect to terminal points of at least some of said microstrip transmission lines wherein said control devices operate to control the potential on said microstrip transmission lines   e. said characteristic impedance including a resistance-capacitance network coupled to each end of said transmission lines     
     
     
       20. The system of claim 19 wherein said backplane comprises: a multilayer sandwich having at least a voltage plane,   and a ground plane with all of said planes being separated by insulation.   
     
     
       21. In a printed circuit arrangement for pulse operation in the megahertz frequency range which arrangement involves circuit elements including buffers mounted on printed circuit boards and arranged to operate with respect to a common reference potential, and printed conductors connecting the elements together, the combination of: a. a backplane including a ground plane;   b. microstrip lines etched on the surface of said backplane and forming a transmission line with said ground plane;   c. terminating impedances at each end of at least some of said microstrip lines to match the characteristic impedance and wherein said terminating impedances comprise a series resistor-capacitor network coupled between the transmission line and said ground plane with buffers of the tri-state type; and   d. wherein said terminating impedances comprise a series resistor-capacitor network coupled between a source of potential and said ground plane with buffers of the open collector type.